package demo;

import java.util.LinkedList;
import java.util.Queue;

/**
 * 两个队列  实现栈
 */
class MyStack {

    Queue<Integer> qu1 ;
    Queue<Integer> qu2 ;
    public int usedSize;
    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }

    //入栈
    public void push(int x) {
        if(!qu1.isEmpty()) {
            qu1.offer(x);
        }else if(!qu2.isEmpty()) {
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
        usedSize++;
    }
    //出栈
    public int pop() {
        if(empty()) {
            return -1;
        }
        //size会变化
        if(!qu1.isEmpty()) {
            int curSize = qu1.size();
            for (int i = 0; i < curSize-1; i++) {
                qu2.offer(qu1.poll());
            }
            usedSize--;
            return qu1.poll();
        }else {
            int curSize = qu2.size();
            for (int i = 0; i < curSize-1; i++) {
                qu1.offer(qu2.poll());
            }
            usedSize--;
            return qu2.poll();
        }
    }
    //就是peek
    public int top() {
        if(empty()) {
            return -1;
        }
        //size会变化
        if(!qu1.isEmpty()) {
            int curSize = qu1.size();
            int ret = -1;
            for (int i = 0; i < curSize; i++) {
                ret = qu1.poll();
                qu2.offer(ret);
            }
            return ret;
        }else {
            int curSize = qu2.size();
            int ret = -1;
            for (int i = 0; i < curSize; i++) {
                ret = qu2.poll();
                qu1.offer(ret);
            }
            return ret;
        }
    }
    //空
    public boolean empty() {
        return usedSize == 0;
    }

    public boolean empty2() {
        return qu1.isEmpty() && qu2.isEmpty();
    }

}